Heres the video http://www.prostarproductions.com/Flex%20network%20problem.mp4
6600 on 2.1.33 directly connected to computer.
I get same results on 2 other computers and a laptop, I have to think this is a software problem.
Tried many different cables, direct connect and go thru switch.
This video was taken on a freshly win 10 install and 2.1.33 fresh install onto yet another computer.
So does your flex do it too?
I reported the same problem about a year ago, Havn't seen any SSDR updates to correct the issue. https://community.flexradio.com/flexradio/topics/ssdr-waterfall-stutter-on-startup
There is a naff workaround by downgrading the NIC from 1Gbps to 100Mbps on the direct Ethernet connection to the Flex. It worked for me after a lot of experimenting.